It looks like you dont need to print the card backas at all, you could also just print the 13 pages of card fronts and leave the backs blank, and not bother with sleeves. I think that's what I'll be doing.
Love that art work BTW!
You are right. The back was just included to be prettier and to help separate the different type of cards. However, I would suggest to print 1 pages of the backs (for example page 16) and include it as another summary card. It's helpful while playing the game. I'll add your suggestion as another Alternative. Thanks!